Field of the Invention
The present invention relates to the technical field of cosmetics, especially that of sunscreen cosmetic compositions. More particularly, the present invention relates to the use, in cosmetic compositions containing pigment particles as UV-filtering agents, of new additives as agents improving the UV-absorbing capacities of said compositions. The present invention also relates to sunscreen compositions containing such agents.
Description of the Related Art
It is known that UV-B rays with wavelengths comprised between 280 nm and 320 nm cause erythema and skin burns. It is also known that UV-A rays with wavelengths comprised between 320 nm and 400 nm, which are responsible for skin tanning, are also likely to induce an alteration thereof, particularly in the case of sensitive skin or skin that is constantly exposed to solar radiation. It is therefore desirable that sunscreen cosmetic compositions be able to filter UV-A and UV-B radiations.
Many cosmetic compositions intended for solar protection of the skin against UV-A and/or UV-B radiations have been proposed to date. Such compositions traditionally contain a UV radiations filtering agent. There are primarily two categories of UV radiations filtering agents: organic filters and pigment type filters such as the metallic oxides, for example, titanium dioxide and zinc oxide.
In this technical context, a certain number of documents of the prior art describe the use of additives in order to promote the cosmetic properties of the sunscreen compositions that contain them. For example, the use of cross-linked emulsifying copolymers of the C10-C30 alkyl acrylic/acrylate acid type, such as those known as Pemulen® or Carbopol®, the use of which is now very widespread, may be cited.
It turns out however that with certain copolymers of the prior art, the improvement of the compositions cosmetic properties is done at the expense of the UV-absorbing performances of these compositions. Thus, another part of the prior art describes the use of additives whose purpose is, in addition to obtaining beneficial cosmetic properties, the obtaining of sunscreen compositions having protection indexes that are greater than that which may be obtained with the same filtering system.
In this connection, mention can be made of document EP 0 685 227 (L'Oréal) which describes the use of specific polymers to improve the solar protection properties of these compositions. The polymers mentioned in this document are of the cross-linked terpolymer of the methacrylic acid/ethyl acrylate/steareth-10 allyl ether and acrylic acid/vinyl acetate copolymer types.
Also cited is document EP 1 142 564 (L'Oréal) which describes the association in a cosmetic composition of the oil-in-water emulsion type of a particular mixture of polyethylenes with an organic solar protection system.
Other prior art documents describe the use of composite particles whose purpose is both to provide better protection against radiation and to obtain a composition having particular textural properties. Among these, the patent application EP 1 388 550 (Kao Corp) relating to the use of particles consisting of a metal oxide particle coated with a siliconated or fluorinated compound, may be cited. The application FR 2 970 172 (L'Oréal) may also be cited, in which the composite particles include a matrix and an inorganic UV filter. Such particles are formulated in the presence of a hydrophilic dispersant surfactant agent.
Nevertheless, it must be noted that mineral pigment type for example, titanium dioxide (TiO2), zinc oxide (ZnO), cerium oxide (CeO2) and/or iron oxides (Fe3O4, Fe2O3) or composite mineral pigments, for example particles of coated titanium dioxide or particles of titanium dioxide having undergone one or several surface treatments of chemical, electronic, mechanochemical and/or mechanical nature, are products whose availability is becoming increasingly limited because they rely only on a natural resource. This leads to an increase in their price which is a problem for the formulators of sunscreen compositions.
The inventors therefore sought a solution to this problem of pigment particles availability of mineral pigments type and of coated mineral pigments type. Specifically, the inventors sought a solution aimed at implementing reduced quantities of pigment particles in sunscreen cosmetic compositions without reducing the properties expected of said compositions.
A certain number of the prior art documents describe the implementation of dispersing agents that have the ability to improve the state of pigment dispersions in cosmetic products. Nevertheless, despite the use of dispersing agents in sunscreen cosmetic formulations, the phenomenon of particles flocculation, notably during storage of the cosmetic composition and in the formation of the film on the skin reduces the filtering effectiveness of agents such as TiO2 and/or ZnO.